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26 Jan 2021

Investigation of the antibody landscape in children: SARS-CoV-2 infected children have lower levels of antibodies than adults

Children are less clinically affected by SARS-CoV-2 infection than adults with the majority of cases being mild or asymptomatic and the differences in infection outcomes are poorly understood. The kinetics, magnitude and landscape of the antibody response may impact the clinical severity and serological diagnosis of COVID-19. Thus, a comprehensive investigation of the antibody landscape in children and adults is needed.

This investigation has been conducted by Asmaa Hachim and Niloufar Kavian within Sophie Valkenburg’s team in a pre-print publication published online on January 3rd. The research team tested 254 plasma from 122 children with symptomatic and asymptomatic SARS-CoV-2 infections in Hong Kong. Adult COVID-19 patients and pre-pandemic controls were included for comparison.

Therefore, this is the most comprehensive study to date of the magnitude, specificity and duration of SARS-CoV-2 specific antibodies in children.

The results show that children have lower levels of antibodies to the majority of proteins overall, with minor responses to non-structural proteins. The study highlights that SARS-CoV-2 antibody response in children is highly diverse, which may be an important factor in driving control of SARS-CoV-2 infection.

 

 

Read the publication online: “The SARS-CoV-2 antibody landscape is lower in magnitude for structural proteins, diversified for accessory proteins and stable long-term in children”, medRxiv 2021.01.03.21249180.

12 Jan 2021

Follow-up: Project On Sewage Helps Uncover Nine Infections In Hong Kong

The University of Hong Kong sewage surveillance project involving HKU-Pasteur research teams will extend its screening capacity after successfully uncovering hidden COVID-19 carriers in two housing blocks in Hong Kong. Standard operating procedure are finalised to trigger mandatory testing of all residents in a block if sewage checks reveal two consecutive positive results or two positive results over three days.

Sponsored by the Health and Medical Research Fund (HMRF) under the Food and Health Bureau, this project allowed the collection of more than 300 domestic sewage samples from sewage collection systems in different areas for nucleic acid tests of the new coronavirus SARS-CoV-2. 
 
Since the beginning of the project in October 2020, the team has been able to demonstrate that sewage surveillance could provide early warning of COVID-19 outbreaks, reflecting the overall spread of virus in the community. It also helps tracking the development trend of community outbreak.
 
 
 
 

12 Jan 2021

SARS-CoV-2 Infection Elicits Robust Neutralizing Antibody Titres In Most Individuals

Prof Leo Poon and Prof Malik Peiris published in Nature Communications the results of their study on neutralizing antibody titres in SARS-CoV-2, concluding that the infection elicits robust neutralizing antibody titres in most individuals.
 
They proceeded by testing 293 sera from an observational cohort of 195 reverse transcription polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections collected from 0 to 209 days after onset of symptoms.
 
Introduction:
Many studies have reported antibody responses in COVID-19 patients using ELISA or other binding assays, but there are fewer reports using virus neutralization tests. Patients with COVID-19 infection develop detectable SARS-CoV-2 neutralizing antibody responses with some having detectable antibody at the end of the 1st week of illness, and almost all having neutralizing antibody after 4 weeks of illness. The magnitude of the antibody responses and the proportion of patients developing antibody responses have varied. Severely ill patients are reported to have higher peak neutralizing antibody titers. 
 
The methods used for detecting neutralizing antibody has also varied. These include the use of pseudoparticle neutralization (ppNT), microneutralization, fluorescent focus reduction assays, microneutralization assays, and plaque reduction neutralization tests (PRNT). Pseudoparticle neutralization tests are convenient and do not require bio-safety level 3 containment, but it is not clear how closely different types of virus pseudoparticles expressing SARS-CoV-2 spike protein mimics authentic virus, or how results from one pseudoparticle assay compares with another. 
 
Even with neutralization of live virus, microneutralization tests were found to be less sensitive than plaque reduction neutralization assays, which are regarded as the “gold-standard” for neutralizing antibody testing. The major outstanding question is the duration of these neutralizing antibody responses. There are reports of rapid waning of antibody with some reports claiming that a third of patients have lost pseudoparticle neutralizing antibody by around 1–2 months after onset of illness. If true, such findings have major implications for the duration of protective immunity from reinfection, and the likely success of vaccination in prevention from reinfection and disease. It is therefore essential that the duration of neutralizing antibody responses are assessed using live virus neutralization assays.
 
 
 
 
Fig. 1: Antibody responses (PRNT90) in COVID-19 patients by days after illness onset and severity, Hong Kong (n = 293 samples).
The black lines showed the fitted values and gray areas showed the 95% confidence intervals. Neutralization tests were carried out in duplicate.
 
Fig. 2: Antibody responses (PRNT50) in COVID-19 patients by days after illness onset and severity, Hong Kong (n = 293 samples).
The black lines showed the fitted values and gray areas showed the 95% confidence intervals. Neutralization tests were carried out in duplicate.